This invention relates to an antimicrobial compound useful as a drug for humans, animals or fishes or an antimicrobial preservative and an antimicrobial agent or preparation containing the same.
Since the discovery of Norfloxacin, improvements have been added to synthetic quinolone antimicrobial agents in antimicrobial activity and in pharmacokinatics, and many compounds have been launched for clinical use as a chemotherapeutic agent effective on all most all systemic infectious diseases.
However, low sensitive bacteria resistant to the synthetic quinolone antimicrobial agents hive recently been increasing in the clinical field. For example, bacteria resistant to drugs other than synthetic quinolone antimicrobial agents have come to acquire resistance to synthetic quinolone antimicrobial agents, as exemplified by Staphylococcus aureaus insensitive to xcex2-lactam antibiotics (MRSA). Therefore, more effective drugs have been keenly demanded in the field of clinics.
Further, it has been revealed that synthetic quinolone antimicrobial agents tend to involve side effects, such as induction of convulsion in a combined use with a non-steroid antiinflammatory agent, and phototoxicity. Therefore, development of safer synthetic quinolone antimicrobial agents has been sought.
In the light of these circumstances, the inventors have conducted extensive investigation for the purpose of providing excellent compounds fulfilling the above demands. As a result, they have found that cis-substituted aminocyclopropane derivatives represented by the following formula (I) and their salts have broad antimicrobial spectra, exhibiting potent antimicrobial activity particularly on Gram positive bacteria, especially quinolone-resistant bacteria including MRSA, and also show satisfactory in pharmacokinatics and safety.
The present invention relates to a compound represented by formula (I) shown below, its salt and their hydrates: 
wherein R1 and R2 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms which may be substituted with one or more substituents selected from the group consisting of a hydroxyl group, a halogen atom, an alkylthio group having 1 to 6 carbon atoms, and an alkyloxy group having 1 to 6 carbon atoms; n represents an integer of 1 to 3; Q represents a partial structure having formula: 
wherein R3 represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, a halogenoalkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, an alkoxyl group having 1 to 6 carbon atoms, or an alkylamino group having 1 to 6 carbon atoms; R4 represents a hydrogen atom or an alkylthio group having 1 to 6 carbon atoms; R3 and R4 may be taken together with part of the mother skeleton to which they are bonded to form a cyclic structure that may contain a sulfur atom as a ring constituting atom and/or may be substituted with an alkyl group having 1 to 6 carbon atoms; R5 represents a hydrogen atom, an amino group, a hydroxyl group, a thiol group, a halogenomethyl group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms or an alkoxyl group having 1 to 6 carbon atoms, in which the amino group may be substituted with one or more substituents selected from the group consisting of a formyl group, an alkyl group having 1 to 6 carbon atoms, and an acyl group having 2 to 5 carbon atoms; X1 represents a halogen atom or a hydrogen atom; and A represents a nitrogen atom or a partial structure represented by formula (II): 
wherein X2 represents a hydrogen atom, an amino group, a halogen atom, a cyano group, a halogenomethyl group, a halogenomethoxyl group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, or an alkoxyl group having 1 to 6 carbon atoms, in which the amino group may be substituted with one or more substituents selected from the group consisting of a formyl group, an alkyl group having 1 to 6 carbon atoms and an acyl group having 2 to 5 carbon atoms; and X2 and R3 may be taken together with part of the mother skeleton to which they are bonded to form a cyclic structure that may contain an oxygen atom, a nitrogen atom or a sulfur atom as a ring constituting and/or may be substituted with an alkyl group having 1 to 6 carbon atoms;
and Y represents a hydrogen atom, a phenyl group, an acetoxymethyl group, a pivaloyloxymethyl group, an ethoxycarbonyl group, a choline group, a dimethylaminoethyl group, a 5-indanyl group, a phthalidinyl group, a 5-alkyl-2-oxo-1,3-dioxol-4-ylmethyl group, a 3-acetoxy-2-oxobutyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxymethyl group having 2 to 7 carbon atoms, or a phenylalkyl group having 1 to 6 carbon atoms in the alkyl moiety thereof;
and the two substituents on the cyclopropane ring, 
are in a cis-configuration.
The present invention also relates to:
a compound of formula (I), wherein Q is a partial structure represented by formula: 
wherein R3, R4, R5, X1, X2, and Y are as defined above, or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I), wherein Q is a 6-carboxy-9-fluoro-2,3-dihydro-3-(S)-methyl-7-oxo-7H-pyrido[1,2,3-de][1,4]benzoxazin-10-yl group of formula: 
or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I), wherein Q is a 8-amino-6-carboxy-9-fluoro-2,3-dihydro-3-(S)-methyl-7-oxo-7H-pyrido[1,2,3-de][1,4]benzoxazin-10-yl group of formula: 
or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I), wherein Q is a 5-amino-3-carboxy-6-fluoro-1-[2-(S)-fluoro-1-(R)-cyclopropyl]-1,4-dihydro-8-methoxyl-4-oxoquinolin-7-yl group of formula: 
or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I), wherein Q is a 5-amino-3-carboxy-6-fluoro-1-[2-(S)-fluoro-1-(R)-cyclopropyl]-1,4-dihydro-8-methyl-4-oxoquinolin-7-yl group of formula: 
or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I), wherein Q is a 3-carboxy-6-fluoro-1-[2-(S)-fluoro-1-(R)-cyclopropyl]-1,4-dihydro-8-methoxyl-4-oxoquinolin-7-yl group of formula: 
or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I), wherein n is 2, or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I), wherein R1 and R2 are each a hydrogen atom, or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I), wherein R3 is a halogenocyclopropyl group, or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I), wherein R3 is a 1,2-cis-2-halogenocyclopropyl group, or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I), wherein R3 is a stereochemically pure substituent, or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I), wherein R3 is a (1R,2S)-2-halogenocyclopropyl group, or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I), wherein R3 is a (1R,2S)-2-fluorocyclopropyl group, or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I), wherein X1 is a halogen atom, or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I), wherein X1 is a fluorine atom, or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (I) which is a stereochemically pure compound, or a salt or hydrate thereof or a hydrate of the salt;
5-amino-7-{3-[(1S,2S)-2-aminocyclopropyl]-1-pyrrolidinyl}-6-fluoro-1-[(1R,2S)-2-fluorocyclopropyl]-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acid or a salt or hydrate thereof or a hydrate of the salt;
a drug containing any of the above-described compounds, hydrates thereof, salts thereof, and hydrates of the salts as an active ingredient; and
an antimicrobial agent containing any of the above-described compounds, hydrates thereof, salts thereof, and hydrates of the salts as an active ingredient.
The present invention also relates to a compound represented by formula (VI) shown below, a salt or hydrate thereof, and a hydrate of the salt: 
wherein R1 and R2 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms which may be substituted with one or more substituents selected from the group consisting of a hydroxyl group, a halogen atom, an alkylthio group having 1 to 6 carbon atoms, and an alkyloxy group having 1 to 6 carbon atoms; one of R1 and R2 may be a protective group for amino group; n represents an integer of 1 to 3; Qxe2x80x2 represents a hydrogen atom or a protective group for amino group; and the two substituents on the cyclopropane ring, 
are in a cis-configuration;
a compound of formula (VI), wherein the protective group for amino group is selected from the group consisting of a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted aralkyloxycarbonyl group, a substituted or unsubstituted acyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, and a substituted silyl group, or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (VI), wherein the protective group for amino group is selected from the group consisting of a t-butoxycarbonyl group, a 2,2,2-trichloroethoxycarbonyl group, a benzyloxycarbonyl group, a p-methoxylbenzyloxycarbonyl group, a p-nitrobenzyloxycarbonyl group, an acetyl group, a methoxylacetyl group, a trifluoroacetyl group, a chloroacetyl group, a pivaloyl group, a formyl group, a benzoyl group, a t-butyl group, a benzyl group, a p-nitrobenzyl group, a p-methoxybenzyl group, a triphenylmethyl group, a methoxymethyl group, a t-butoxymethyl group, a tetrahydropyranyl group, a 2,2,2-trichloroethoxymethyl group, a trimethylsilyl group, an isopropyldimethylsilyl group, a t-butyldimethylsilyl group, a tribenzylsilyl group, and a t-butyldiphenylsilyl group, or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (VI), wherein Qxe2x80x2 and one of R1 and R2 are different protective groups for amino group, or a salt or hydrate thereof or a hydrate of the salt;
a compound of formula (VI) which is a stereochemically pure compound, or a salt or hydrate thereof or a hydrate of the salt;
and 1-benzyloxycarbonyl-3-[(1S,2S)-2-t-butoxycarbonylamino-cyclopropyl]pyrrolidine or a salt or hydrate thereof or a hydrate of the salt.
The compound according to the present invention, represented by formula (I): 
namely, formula: 
is described with reference to the substituents thereof.
Substituents R1 and R2 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms which may be substituted with one or more substituents selected from the group consisting of a hydroxyl group, a halogen atom, an alkylthio group having 1 to 6 carbon atoms, and an alkyloxy group having 1 to 6 carbon atoms.
The alkyl group may be a straight-chain or branched having 1 to 6 carbon atoms and preferably is a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. The hydroxyl-substituted alkyl group having 1 to 6 carbon atoms may be a straight-chain or branched and preferably are a hydroxyethyl group and a hydroxypropyl group.
The alkylthio group having 1 to 6 carbon atoms preferably includes a methylthio group and an ethylthio group. The alkyloxy group having 1 to 6 carbon atoms preferably are a methoxyll group and an ethoxyl group.
Substituent R3 represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, a halogenoalkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, an alkoxyl group having 1 to 6 carbon atoms, or an alkylamino group having 1 to 6 carbon atoms.
The alkyl group having 1 to 6 carbon atoms preferably are an ethyl group. The alkenyl group having 2 to 6 carbon atoms preferably are a vinyl group or a 1-isopropenyl group. The halogenoalkyl group having 1 to 6 carbon atoms preferably are a 2-fluoroethyl group. The cycloalkyl group preferably is a cyclopropyl group. The substituent for the cycloalkyl group preferably is a halogen atom, particularly a fluorine atom.
The aryl group which may have a substituent includes a phenyl group and a phenyl group having 1 to 3 substituents selected from the group consisting of a halogen atom (e.g., fluorine, chlorine, and bromine), a lower alkyl group having 1 to 6 carbon atoms, a hydroxyl group, an amino group, a nitro group, a lower alkoxyl group having 1 to 6 carbon atoms, etc., and preferably are a phenyl group, a 2-fluorophenyl group, a 4-fluorophenyl group, 2,4-difluorophenyl group, and a 2-fluoro-4-hydroxyphenyl group.
The heteroaryl group is a substituent derived from an aromatic heterocyclic compound containing at least one hetero atom selected from a nitrogen atom, an oxygen atom and a sulfur atom and includes a pyridyl group and a pyrimidyl group. The substituents on the heteroaryl group preferably are an alkyl group and a halogen atom.
The alkoxyl group having 1 to 6 carbon atoms preferably are a methoxyl group. The alkylamino group having 1 to 6 carbon atoms preferably are a methylamino group.
Substituent R3 is preferably a cycloalkyl group or a halogenocycloalkyl group, still preferably a cyclopropyl group or a 2-halogenocyclopropyl group, in which the halogen atom is preferably a fluorine atom.
Substituent R4 represents a hydrogen atom or an alkylthio group having 1 to 6 carbon atoms, or R3 and R4 may be taken together with part of the mother skeleton (that is, so as to the nitrogen atom to which R3 is bonded and the carbon atom to which R4 is bonded to are involved) to form a cyclic structure. The ring formed may contain a sulfur atom as a ring constituting atom. It may be substituted with an alkyl group having 1 to 6 carbon atoms. The ring can be a 4- to 6-membered ring and may be saturated, partially saturated or unsaturated. The alkylthio group having 1 to 6 carbon atoms preferably are a methylthio group and an ethylthio group.
The condensed ring structure thus formed includes the following structures. 
X1 represents a halogen atom or a hydrogen atom.
As for the halogen atom, a fluorine atom is preferable.
X1 preferably is a fluorine atom or a hydrogen atom.
Where A is a partial structure of formula (II): 
X2 represents a hydrogen atom, an amino group, a halogen atom, a cyano group, a halogenomethyl group, a halogenomethoxyl group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, or an alkoxyl group having 1 to 6 carbon atoms. The amino group may have one or more substituents selected from the group consisting of a formyl group, an alkyl group having 1 to 6 carbon atoms and an acyl group having 2 to 5 carbon atoms.
The alkyl group may be a straight-chain or branched having 1 to 6 carbon atoms and preferably are a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. The alkenyl group may be a straight-chain or branched having 2 to 6 carbon atoms and preferably is a vinyl group. The alkynyl group may be a straight-chain or branched having 2 to 6 carbon atoms and preferably is an ethynyl group. The halogenomethyl group may contain 1 to 3 halogen atoms, and the halogen atom thereof is preferably a fluorine atom. The alkoxyl group may be those having 1 to 6 carbon atoms and preferably is a methoxyl group. The halogenomethoxyl group may have 1 to 3 halogen atoms, and the halogen atom thereof is preferably a fluorine atom.
R3 and X2 may be taken together with part of the mother skeleton (that is, so as to the nitrogen atom to which R3 is bonded and the carbon atom to which x2 is bonded are involved) to form a cyclic structure that may contain an oxygen atom, a nitrogen atom or a sulfur atom as a ring constituting atom and/or may be substituted with an alkyl group having 1 to 6 carbon atoms. The cyclic structure can be a 4- to 7-membered ring and may be saturated, partially saturated or unsaturated.
The condensed ring structure thus formed includes the following structures. 
A 6-carboxy-2,3-dihydro-3-(S)-methyl-7-oxo-7H-pyrido[1,2,3-de][1,4]benzoxazin-10-yl group is particularly preferred of them.
Substituent R5 represents a hydrogen atom, an amino group, a hydroxyl group, a thiol group, a halogenomethyl group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, -an alkynyl group having 2 to 6 carbon atoms or an alkoxyl group having 1 to 6 carbon atoms, in which the amino group may be substituted with one or more substituents selected from the group consisting of a formyl group, an alkyl group having 1 to 6 carbon atoms, and an acyl group having 2 to 5 carbon atoms.
The alkyl group can be a straight-chain or branched having 1 to 6 carbon atoms and preferably is a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. The alkenyl group can be a straight-chain or branched having 2 to 6 carbon atoms and preferably is a vinyl group. The alkynyl group may be a straight-chain or branched having 2 to 6 carbon atoms and preferably is an ethynyl group. The halogenomethyl group may contain 1 to 3 halogen atoms, and the halogen atom thereof preferably is a fluorine atom. The alkoxyl group can be those having 1 to 6 carbon atoms and preferably is a methoxyl group.
The acyl group having 2 to 5 carbon atoms which may be a substitutent for the amino group preferably are an acetyl group, a propanoly group and a butanoyl group.
Where X2 or R5 is an amino group, a hydroxyl group or a thiol group, these groups may be protected by commonly used protective groups, such as a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted aralkyloxycarbonyl group, a substituted or unsubstituted acyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, and a silyl group substituted with an alkyl group or an aralkyl group (they may be the same or different).
Specific examples of the protective group include substituted or unsubstituted alkoxycarbonyl groups, e.g., a t-butoxycarbonyl group and a 2,2,2-trichloroethoxycarbonyl group; substituted or unsubstituted aralkyloxycarbonyl groups, e.g., a benzyloxycarbonyl group, a p-methoxybenzyloxycarbonyl group, and a p-nitrobenzyloxycarbonyl group; substituted or unsubstituted acyl groups, e.g., an acetyl group , a methoxyacetyl group, a trifluoroacetyl group, a chloroacetyl group, a pivaloyl group, a formyl group, and a benzoyl group; substituted or unsubstituted alkyl or aralkyl groups, e.g., a t-butyl group, a benzyl group, a p-nitrobenzyl group, a p-methoxybenzyl group, a triphenylmethyl group, and a phenethyl group; ether groups, e.g, a methoxymethyl group, a t-butoxymethyl group, a tetrahydropyranyl group, and a 2,2,2-trichloroethoxymethyl group; and substituted silyl groups, e.g., a trimethylsilyl group, an isopropyldimethylsilyl group, a t-butyldimethylsilyl group, a tribenzylsilyl group, and a t-butyldiphenylsilyl group. The compounds whose substituents are protected by these protective groups are particularly useful as an intermediate for preparing the compounds of formula (I).
Y represents a hydrogen atom, a phenyl group, an acetoxymethyl group, a pivaloyloxymethyl group, an ethoxycarbonyl group, a choline group, a dimethylaminoethyl group, a 5-indanyl group, a phthalidinyl group, a 5-alkyl-2-oxo-1,3-dioxol-4-ylmethyl group, a 3-acetoxy-2-oxobutyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxymethyl group having 2 to 7 carbon atoms, or a phenylalkyl group having 1 to 6 carbon atoms in the alkyl moiety thereof.
The alkyl group having 1 to 6 carbon atoms preferably are a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group and a t-butyl group. The alkoxymethyl group having 2 to 7 carbon atoms preferably are a methoxymethyl group and an ethoxymethyl. The phenylalkyl group having 1 to 6 carbon atoms in the alkyl moiety thereof preferably are a benzyl group and a phenetyl group.
Where A is a partial structure represented by formula (II), a preferable combination of substituents R5 and X2 is that R5 is selected from an amino group, a hydrogen atom, a hydroxyl group, and an alkyl group having 1 to 6 carbon atoms, and X2 is selected from an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, a halogenomethoxyl group, and a hydrogen atom. In a still preferred combination, R5 is an amino group, a hydrogen atom, a hydroxyl group or a methyl group, and X2 is a methyl group, a methoxyl group, a difluoromethoxyl group or a hydrogen atom.
In the above case, X1 preferably is a fluorine atom with respect to R5 and X2. Where X1 and X2 are both a halogen atom, X1 preferably is a fluorine atom, and X2 preferably is a fluorine atom or a chlorine atom.
The compounds according to the present invention are characterized in that the quinolone skeleton has a substituent represented by formula: 
at the 7-position or a corresponding position, namely, the formula that the amino group or alkylamino group: 
and a 4-membered (n=1) to 6-membered (n=3) nitrogen-containing saturated heterocyclic substituent: 
are bonded to the cyclopropyl group.
While the amino moiety and the nitrogen-containing saturated heterocyclic moiety can be in a cis- or trans-configuration with respect to the cyclopropyl group (cyclopropane ring), a cis-configuration shown below is preferred. 
Where n is 2 or 3, the nitrogen-containing saturated heterocyclic moiety and the cyclopropane ring are bonded in two modes to provide isomers. Such isomers are illustrated below, taking the structure wherein n=2 for instance. Similar isomers are produced when n is 3. The present invention is intended to embrace all these isomers under the scope thereof. 
The cyclopropyl moiety may have further substituents, for example, a fluorine atom, a methyl group, an ethyl group, a trifluoromethyl group, etc.
The halogenocyclopropyl group as R3 is then described. The substituent halogen atom includes a fluorine atom and a chlorine atom, with a fluorine atom being preferred.
It is particularly preferred that the substituent halogen atom and the pyridonecarboxylic acid moiety be in a cis-configuration with respect to the cyclopropane ring.
Regardless of stereoisomerism of the 7-positioned substituent, the cis-2-halogenocyclopropyl moiety of R3 makes a pair of antipodes, each of which was observed to exhibit potent antimicrobial activity and high safety.
Where the compound of formula (I) has such a structure that produces diastereomers, it is desirable to administer a compound comprising a pure diastereomer in administration to humans or animals. The language xe2x80x9ca compound comprising a pure diastereomerxe2x80x9d as used herein is construed as including not only a compound containing no other diastereomer at all but a compound containing other diastereomers to such an extent that the compound is recognized to be stereochemically pure as a whole. In other words, it is construed as meaning that other diastereomers may exist to some extent as long as the existence gives no substantial influence on physiological activities or physicochemical constants.
The language xe2x80x9cstereochemically purexe2x80x9d as used herein is intended to mean that a compound comprises only one of its stereoisomers ascribed to its asymmetric carbon atom. The latitude of the term xe2x80x9cpurexe2x80x9d in xe2x80x9cpure diastereomerxe2x80x9d also applies here.
The pyridonecarboxylic acid derivative of the present invention may present in either a free form or a form of an acid addition salt or a carboxylic acid salt. Acid addition salts include inorganic acid salts, such as a hydrochloride, a sulfate, a nitrate, a hydrobromide, a hydroiodide, and a phosphate; and organic acid salts, such as an acetate, a metanesulfonate, a benzenesulfonate, a toluenesulfonate, a citrate, a maleate, a fumarate, and a lactate.
The carboxylic acid salts include inorganic salts and organic salts, such as alkali metal salts, e.g., a lithium salt, a sodium salt, and a potassium salt; alkaline earth metal salts, e.g., a magnesium salt and a calcium salt; an ammonium salt; a triethylamine salt, an N-methylglucamine salt, and a tris-(hydroxymethyl)aminomethane salt.
The free pyridonecarboxylic acid derivatives, acid addition salts thereof, and carboxylic acid salts thereof may be present as a hydrate.
On the other hand, quinolone derivatives with the carboxylic acid moiety thereof having an ester form are useful as an intermediate for synthesis or a pro-drug. For example, alkyl esters, benzyl esters, alkoxylalkyl esters, phenylalkyl esters, and phenyl esters are useful as synthetic intermediates.
Esters which can be used as pro-drugs are those which are susceptible to an in vivo cleavage to form a free carboxylic acid, including an acetoxymethyl ester, a pivaloyloxymethyl ester, an ethoxycarbonyl ester, a choline ester, a dimethylaminoethyl ester, a 5-indanyl ester, a phthalidinyl ester, a 5-alkyl-2-oxo-1,3-dioxol-4-ylmethyl ester, and oxoalkyl esters, such as a 3-acetoxy-2-oxobutyl ester.
The compound of formula (I) can be prepared through various processes. A preferred process comprises reacting a compound represented by formula (III): 
wherein X3 represents a leaving group, such as a fluorine atom, a chlorine atom, a bromine atom, an alkylsulfonyl group having 1 to 3 carbon atoms, or an arylsulfonyl group, e.g., a benzenesulfonyl group or a toluenesulfonyl group; Y has the same meaning as in formula (I) or represents a boron-containing group represented by formula (IV):
xe2x80x94B(R6)R7xe2x80x83xe2x80x83(IV)
wherein R6 and R7 each represents a fluorine atom or a lower alkylcarbonyloxy group;
and R3, R4, R5, X1, and X2 are as defined in formula (I), with a compound represented by formula (V): 
wherein R1, R2, and n are as defined in formula (I), except that R1 may be a nitrogen-protective group Rx.
Any protective group generally used in the art can be used as protective group Rx. Examples of useful protective groups include alkoxylcarbonyl groups, e.g., a t-butoxycarbonyl group and a 2,2,2-trichloroethoxycarbonyl group; aralkyloxycarbonyl groups, e.g., a benzyloxycarbonyl group, a p-methoxybenzyloxycarbonyl group, and a p-nitrobenzyloxycarbonyl group; acyl groups, e.g., an acetyl group, a methoxyacetyl group, a trifluoroacetyl group, a chloroacetyl group, a pivaloyl group, a formyl group, and a benzoyl group; alkyl or aralkyl groups, e.g., a t-butyl group, a benzyl group, a p-nitrobenzyl group, a p-methoxybenzyl group, and a triphenylmethyl group; ether groups, e.g, a methoxymethyl group, a t-butoxymethyl group, a tetrahydropyranyl group, and a 2,2,2-trichloroethoxymethyl group; and substituted silyl groups, e.g., a trimethylsilyl group, an isopropyldimethylsilyl group, a t-butyldimethylsilyl group, a tribenzylsilyl group, and a t-butyldiphenylsilyl group, or an acid addition salt thereof.
The resulting compound in which Y is an alkyl group having 1 to 6 carbon atoms, an alkoxymethyl group having 2 to 7 carbon atoms or a phenylalkyl group having 1 to 6 carbon atoms in the alkyl moiety thereof can be converted to the corresponding carboxylic acid by hydrolysis under an acidic or basic condition commonly used for hydrolysis of carboxylic acid esters. The protective group, if any, is removed under properly selected conditions to obtain a desired compound (I).
The compound obtained by the substitution reaction between the compound (III) wherein Y is the group (IV) and the compound (V) can be converted to the corresponding carboxylic acid by treatment with an acidic or basic compound.
The substitution reaction between the compound of formula (III) and the compound of formula (V) is carried out with or without a solvent. The solvent, if used, is not limited as long as it is inert under the reaction conditions. Suitable solvents include dimethyl sulfoxide, pyridine, acetonitrile, ethanol, chloroform, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, tetrahydrofuran, water, and 3-methoxybutanol. These solvents may be used as a mixture thereof.
The reaction is usually performed at room temperature to 200xc2x0 C., preferably 25 to 150xc2x0 C., for 0.5 to 48 hours. The reaction usually completes in about 0.5 to 2 hours. It is advantageous to conduct the reaction in the presence of an acid acceptor, such as an inorganic base (e.g., an alkali metal or alkaline earth metal carbonate or hydrogencarbonate) or an organic base (e.g., triethylamine, pyridine or 1,8-diazabicycloundecene).
The compound of formula (V) can be prepared by various processes. A preferred process is shown in Reference Examples hereinafter given, but the process is not limited thereto. Most generally, the compound of formula (V) is prepared by removing the protective group from a compound represented by formula (VI) shown below, in which the nitrogen atom is protected by a protective group Qxe2x80x2. 
wherein R1 and R2 each represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, which may have one or more substituents selected from the group consisting of a hydroxyl group, a halogen atom, an alkylthio group having 1 to 6 carbon atoms, and an alkyloxy group having 1 to 6 carbon atoms; one of R1 and R2 may be an protective group for amino group; n represents an integer of 1 to 3; Qxe2x80x2 represents a protective group for amino group; and the two substituents on the cyclopropane ring, 
are in a cis-configuration.
The compound (VI) may exist in the form of a salt, a hydrate, or a hydrate of the salt. Acid addition salts include inorganic acid salts and organic acid salts. Examples of the inorganic acid salts are a hydrochloride, a sulfate, a nitrate, a hydrobromide, a hydroiodide, and a phosphate. Examples of the organic acid salts include sulfonates, such as a metanesulfonate, a benzenesulfonate, and a toluenesulfonate, and carboxylates, such as an acetate, a citrate, a maleate, a fumarate, and a lactate.
Where Qxe2x80x2 and one of R1 and R2 both represent an protective group for amino group, while they may be the same or different, it is advantageous for the preparation of the compound (I) that these protective groups are different so that they are cleaved under the respective different reaction conditions.
The protective group for amino group as R1 or R2 and Qxe2x80x2 includes substituted or unsubstituted alkoxycarbonyl groups, e.g., a t-butoxycarbonyl group and a 2,2,2-trichloroethoxycarbonyl group; substituted or unsubstituted aralkyloxycarbonyl groups, e.g., a benzyloxycarbonyl group, a p-methoxybenzyloxycarbonyl group, and a p-nitrobenzyloxycarbonyl group; substituted or unsubstituted acyl groups, e.g., an acetyl group, a methoxyacetyl group, a trifluoroacetyl group, a chloroacetyl group, a pivaloyl group, a formyl group, and a benzoyl group; substituted or unsubstituted alkyl or aralkyl groups, e.g., a t-butyl group, a benzyl group, a p-nitrobenzyl group, a p-methoxybenzyl group, and a triphenylmethyl group; ether groups, e.g., a methoxymethyl group, a t-butoxymethyl group, a tetrahydropyranyl group, and a 2,2,2-trichloroethoxymethyl group; and substituted silyl groups, e.g., a trimethylsilyl group, an isopropyldimethylsilyl group, a t-butyldimethylsilyl group, a tribenzylsilyl group, and a t-butyldiphenylsilyl group.
Cis-2-fluorocyclopropylamine comprising a pure isomer, which is preferred for the synthesis of the compound of formula (I) comprising a pure isomer, can be synthesized by, for example, the process described in JP-A-2-231475 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d). Synthesis of the compound of formula (I) comprising a pure isomer from the resulting optically active cis-2-fluorocyclopropylamine derivative can be carried out by, for example, the process described in JP-A-2-231475.
The compounds of the present invention have potent antimicrobial activity and are therefore useful as drugs for humans, animals or fishes, agricultural chemicals, or food preservatives.
For use as drugs for humans, the dose of the compound is in the range of from 50 mg to 1 g, and preferably from 100 mg to 300 mg, per day for an adult.
For veterinary use, the dose is generally in the range of from 1 to 200 mg, and preferably from 5 to 100 mg, per kg of body weight per day while varying depending on the purpose of administration (for therapy or for prevention), the kind and the size of the animal, the kind of the pathogenic organisms, and severity of symptom.
The above-mentioned daily dose is given once a day or in 2 to 4 divided doses. If necessary, a daily dose may exceed the above-specified range.
The compounds according to the present invention are active on a broad range of microorganisms causing various infectious diseases and effective to prevent, alleviate or cure diseases caused by these pathogens.
Examples of bacteria or bacterium-like microorganisms on which the compounds of the invention are effective include staphylococci, Streptococcus pyogenes, Streptococcus haemolyticus, Streptococcus faecalis, Streptococcus pneumoniae, peptostreptococci, Neisseria gonorrhoeae, Escherichia coli, Citrobacter sp., Shigella sp., Klebsiella pneumoniae, Enterobacter sp., Serratia sp., Proteus sp., Pseudomonas aeruginosa, Haemophilus influenzae, Acinetobacter sp., Campylobacter sp., and Chlamydozoon trachomatis. 
Diseases which are caused by these pathogens include folliculitis, furuncle, carbuncle, erysipelas, phlegmon, lymphangitis/lymphadenitis, felon, subcutaneous abscess, spiradenitis, acne agminata, infectious atheroma, perianal abscess, mastadenitis, superficial secondary infections after trauma, burn or surgery trauma, pharyngolaryngitis, acute bronchitis, tonsillitis, chronic bronchitis, bronchiectasis, diffuse panbronchiolitis, secondary infections of chronic respiratory diseases, pneumonia, pyelonephritis, cystitis, prostatitis, epididymitis, gonococcal urethritis, non-gonococcal urethritis, cholecystitis, cholangitis, bacillary dysentery, enteritis, adnexitis, intrauterine infections, bartholinitis, blepharitis, hordeolum, dacryocystitis, tarsadenitis, keratohelcosis, otitis media, sinusitis, paradentosis, pericoronitis, gnathitis, peritonitis, endocarditis, septicemia, meningitis, and skin infections.
The compounds of the present invention are also effective on various microorganisms causing veterinary diseases, such as those belonging to the genera Escherichia, Salmonella, Pasteurella, Haemophilus, Bordetella, Staphylococcus, and Mycoplasma. Illustrative examples of the veterinary diseases include those of fowl, such as colibacillosis, pullorum disease, avian paratyphosis, fowl cholera, infectious coryza, staphylomycosis, and mycoplasmosis; those of pigs, such as colibacillosis, salmonellosis, pasteurellosis, hemophilus infections, atrophic rhinitis, exudative epidermitis, and mycoplasmosis; those of cattle, such as colibacillosis, salmonellosis, hemorrhagic septicemia, mycoplasmosis, bovine contagious pleuropneumonia, and bovine mastitis; those of dogs, such as colisepsis, salmonellosis, hemorrhagic septicemia, pyometra, and cystitis; those of cats, such as exudative pleurisy, cystitis, chronic rhinitis, and hemophilus infections; and those of kittens, such as bacterial diarrhea and mycoplasmosis.
Dosage forms of pharmaceutical preparations containing the compound of the present invention are appropriately selected according to the administration route and can be prepared by conventional preparation methods. Examples of dosage forms for oral administration include tablets, powders, granules, capsules, solutions, syrups, elixirs, and oily or aqueous suspensions.
Injectable preparations may contain adjuvants, such as stabilizers, antiseptics, and solubilizers. The injectable solution which may contain these adjuvants may be put into a container and solidified by, for example, lyophilization to prepare a solid preparation which is dissolved on use. The container may contain either a single dose or multiple doses.
Preparations for external application include solutions, suspensions, emulsions, ointments, gels, creams, lotions, and sprays.
Solid preparations may contain, in addition to the active compound, pharmaceutically acceptable additives. For example, the active compound is mixed with additives selected according to necessity from among fillers, extenders, binders, disintegrators, absorption accelerators, wetting agents, and lubricants and formulated into solid preparations.
Liquid preparations include solutions, suspensions, and emulsions. They may contain adjuvants, such as suspending agents, emulsifiers, and so forth.
The compound can be administered to animals orally either directly or by mixing with feedstuff, or in a dissolved form directly given to animals or by mixing with water or feedstuff or non-orally by injection.
For veterinary use, the compound can be formulated into powders, fine granules, soluble powders, syrups, solutions, and injections according to the customary methods in the art.
Formulation Examples are shown below.